Apparently most or all ASUS boards do not allow undervolting p3 and p4 CPUs, they only allow overvolting for overclockers (see the recent Asus P4PE thread).

Since most CPUs are now way overpowered for a home theater PC that's only doing playback, I was thinking of undervolting and underclocking.

Anyone know of p3 or p4 motherboards that undervolt and underclock? Have you done this yourself?

Of course I can always buy some old 815 / BX motherboard and a "slow" p3, but wouldn't an underclocked tualatin celeron 1.2 run cooler than a coppermine p3 or celeron at 800 MHz?

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ADDENDUM by MIKEC: Dave, sorry to hijack your thread, but I think you'll find the intent is perfectly in line with yours... :wink:

A new page called Undervoltable Motherboards has been added to the Recommended Section. This is a short starting list of undervolt-friendly motherboards that will be expanded over time. How quickly this happens depends on how much you help. You can each help a great deal.

The simple fact is that Vcore adjustments are usually not covered in specifications, and often, not even in manuals. In many cases, the only way to know for sure is to go into the BIOS of the motherboard and check the Vcore range available in the CPU frequency/voltage setup menu. Each and every one of you has at least one motherboard, the one in your computer. Most of you have two -- one at home and one at work. Just do a quick check on the BIOS CPU voltage adjustment range of your own PCs and report on any motherboard that provides at least a -0.2V setting from default Vcore setting.

Please submit the information to this thread. I will periodically collect the info and add it to the list below. With everyone's cooperation, we will soon have a large and useful list of undervolt friendly motherboards. If the list gets big enough, we may even divide it up into handy CPU and/or chipset categories.

_________________"It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn't feel like a giant. I felt very, very small. " -- Neil Armstrong

I'm a big PIII Tualatin/Celeron Tualatin fan and feel that these are the perfect CPUs for quiet systems. They run really cool and are very low wattage. I've been wanting to try and run them undervolted. I've always used an Asus Tusl2-C MoBo for my PIII/Tualeron stuff, it's a great board. Very stable, good OCer and lots of features but it won't undervolt. Bummer.

I finally got ahold of a couple of Abit ST6's. These are pretty much considered the "Top-Dog" when it comes to PIII Tualatin/Celeron Tualatin OCing and they happen to be able to undervolt as well. With this board I'm running my PIII-S 1.4Ghz at 1.3V. Default Vcore is 1.45V so this is about a 10% reduction in Vcore. This runs 100% stable at 1.3v. I've stability tested it several times by running Prime95 for 24hr sessions with zero errors. The difference in the full-load temps between default Vcore and the lower Vcore is just about 6C! My max CPU temp under full Prime95 load at 1.3V runs about 43C, at default Vcore load temp is about 48-49C. Damn, pretty schweet, huh?

I'm quite certian that you could get similar results with a Tualatin Celeron running at lower Vcore too. I can run my 1.1A Tualeron at 133FSB (1.463Ghz) on default Vcore. Seems to me that it would run at default speed on much lower Vcore, right?

Rot's 'o Ruck finding an ST6 though. Like most Socket 370 I815 boards they're not made any more. They are not available new anywhere that I've seen for the last 4-6 months. You can occaisionally find a used one on egay but they're hideously expensive, usually well over $150.

Some 815 alternatives to look at (that are available new) might be the Soyo SY-TISU and the EPoX EP-3PTA. They are both overclockable but I can't find out if they undervolt.

Well, how about PIV stuff?

All these guys are getting 600+ mhz OCs at default Vcore, you'd think there'd be all kinds of headroom to run at stock speed + lower Vcore, right? Too bad you can't find out. I build a lot of PIV-based systems for people (it's my side-job) and have never found a Socket 478 board that will allow undervolting the CPU. Abit, Asus, EPoX, Gigabyte - no board that I've used from these manufacturers allows undervolting, and you can't even find out if it's an option in the BIOS even if you look at the pdf manuals available online.

There may be a way to for undervolting by default on both PIII/Celeron Tualatins and PIV Northwoods. The guys over at Overclockersforums have done a lot of experimenting with raising the default Vcore by wrapping the CPU pins with fine wire to short-together various combinations of pins. By doing this they force a higher default Vcore so they don't have problems as they're first booting up. I think there may also be pin combinations that give a lower Vcore as well. There's some big, stickied threads in the OCforums Intel section about this issue. It's known as "vidpinning" It might be worth a read if you're serious about doing this but can't find a board that will undervolt. If I hadn't got an ST6 I'd be messing with it myself.

Undervolting my PIII-S has been a very satisfying experience. It's allowed me to run a very powerful CPU with very quiet cooling at very low temps. I'd recommend that more people look into this area.

D'oh! But thanks for the information. Hunting for a ST6 gives me one more option to choose from along with slow coppermine and the new C3 Epia boards.

It's a shame there isn't enough of a market for slower / quiet motherboards, then we might see the P3-M and Centrino available on desktop boards.

_________________"It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn't feel like a giant. I felt very, very small. " -- Neil Armstrong

Your comment about Asus boards being undervolt-unfriendly extends to their socket-A boards, at least if the A7V266 is any indication. I had a chance to examine this board in detail recently. The lowest Vcore that can be selected for any socket-A cpu is 1.675V, which is hardly 0.05V below default. Pretty pathetic.

My old ABIT KT7A-R board has a Vcore range from 1.1V to ~2V in 0.05V increments. Have not seen what current ABIT boards do.

I think you are right about many P4 boards. An MSI board I tried 6 mos ago (can't recall which), an Asus board and an Intel board (of course) all had no undervolting capability.

However these do:

AOpen AX4GE Max -- 1.1V to 1.95V
Gigabyte GA-81RXP -- 1.1V to 1.85V

Whether this means other models in the above lines generally provide undervolting is not clear. Certain, it is not often mentioned in literature or manuals.

The oc-friendly BX-based boards generally allowed undervolting, though as Ralf mentioned, they are difficult to source now.

Can others please share their experience about undervoltable motherboards here? The info gathered could be used to assemble a recommended mobo list, which would further PC silencing for everyone.

My current chip appears to be stable down to 1.20 volts. Reducing cpu voltage from 1.40 volts to 1.20 lowers idle cpu temperature from 54°C to 47°C in a virtually-silent, very low airflow system. Ambient temperature is 22.7°C.

I agree that the PIII series, especially the S variation, offers great opportunity for low-noise systems.

Very cool. The TISU is one of the few i815 Socket 370 boards that is actually available (for $65 with free shipping from Newegg). Sounds like this would be a great start to a silent PC project. This board plus a $45 1.1A Tualatin Celeron with the retail heatsink fan running at 7 or 5 volts and you're on your way.

johnc wrote:

I agree that the PIII series, especially the S variation, offers great opportunity for low-noise systems.

John Coyle

You betcha! That's why I took the opportunity to buy another PIII-S 1.4 CPU yseterday. It's the exact same stepping as my current CPU that runs so well at low Vcore. You never know when Intel will stop production of these.

<<Intel says default Vcore for the PIII-S is 1.45V. Are you taking your Vcore reading from BIOS hardware monitor or Windows software? If so, maybe this board undervolts. >>

The "1.40 volts = default" idea came from the fact that MotherBoardMonitor indicated that the cpu core voltage was 1.39 volts before I made any modification. With the cpu core adjusted in BIOS to 1.20 volts, MBM is reading 1.16 volts. It is surely possible that either the motherboard undervolts slightly or that the Windows monitoring software (MBM) is slightly inaccurate.

At any rate, this motherboard does provide very flexible cpu voltage adjustment.

<<Intel says default Vcore for the PIII-S is 1.45V. Are you taking your Vcore reading from BIOS hardware monitor or Windows software? If so, maybe this board undervolts. >>

The "1.40 volts = default" idea came from the fact that MotherBoardMonitor indicated that the cpu core voltage was 1.39 volts before I made any modification. With the cpu core adjusted in BIOS to 1.20 volts, MBM is reading 1.16 volts. It is surely possible that either the motherboard undervolts slightly or that the Windows monitoring software (MBM) is slightly inaccurate.

At any rate, this motherboard does provide very flexible cpu voltage adjustment.

John Coyle

I suspect that your MoBo is undervolting. Some boards undervolt (a lot of Abits have this tendancy) and some overvolt (Asuses are known for this). It's no biggy unless you're near the min or max Vcore for your CPU. Just use a software monitoring program to keep track of Vcore in Windows and you'll be fine.

I didn’t see SilentBios or SilentTek with this board. It is $81, delivered, from Newegg.

My understanding is that the AMD Thoroughbred chip comes unlocked and ready for undervolting. The Thoroughbred XP1700+ (0.13 micron process, 1.5v core, 49 watts) sells for $49.99, delivered, from Newegg. This is the OEM chip only, with no fan or heatsink.

Thanks very much for the info johnc. One of my friends is ready to buy a system, and this tips the hand strongly towards Aopen for us. We have been thinking about underclocking/undervolting for a while. Now it's too bad you can't set the clock/vcore on the fly from inside Window$. Bios still kinda sucks in some respects.
I like the looks of Aopen's software support, it really looks like they're trying to support past product. My Asus is still under warranty and they have given up with driver support. BOOOO. Thing locks up all the time, they acknowledge the driver problem, but no fixee. Might as well have bought a cheaper i815 based board, the Nvidia does me little good. When Aopen is retro-tweaking fancy new utils to apply on prior product, I get impressed. I hope their reputation can make them some profit, it would be a welcome break from the bigger-faster-every-week ratrace.

UPDATE: the manual states the lowest cpu vcore is 1.100. after going into my cmos, the lowest setting i saw was 1.65V. this is with an XP 2600+ 333 FSB. im not sure if the manual was misprinted or its CPU related. sorry for any confusion.

Last edited by L4177312 on Sun Jan 26, 2003 11:01 am, edited 2 times in total.

VCORE can be set in range 1.10-1.85Volt but lowest is 1.75Volt from Bios then you have to use undocumented jumper settings on the board. Default VCORE is 1.75V.

I've been running my AMD Athlon XP 1800+ at 1.50V@133MHz without stability problems. 1.45V also seemed to work for some time but then I had some random reboots and thought I'd increase a little. Later I've found out that the early revisions of this board can have problems when you have two memory sticks in mem slots 1&2. If you instead use 1&3 it is more stable. Some kind of impedance match problem on slot 2 according to some usenet sources.

Asus A7V133 supports low voltages, all the way to 1.1V. (I successfully ran 1700XP at 1GHz @ 1.15V for a while, as described in my article).

Too bad Asus completely screwed everyone over with their new products. I contacted them about P4B533's lack of undervolting, and they passed my request to their engineers. Then nothing happened.

What's worse is that Asus forcibly overvolts in some cases. P4B533's DDR memory voltages start from 2.6V and up. The normal voltage is 2.5V and you cannot even use it!

PS: Undervolt-capable P4 motherboards should be perfect for P4-M chips. For example, a P4M/1.8 running at 1600MHz (533fsb with 12x multiplier) at 1.1Vcore would produce only ~20 watts of heat. It might run fanless, because even at full speed/1.3vcore it can tolerate 100C! Underclocked/volted, it could tolerate even higher temps.

It would seem that most of the albatron 845GE and PE range allow voltage changes from 1.100-1.850v from the bios. i would suspect that this applies to most of the albatron boards as they all seem to have the same over(under)clocker aimed system.

i will test it on a reset, unfortunatly that may be a few days before its necessary. am i the only one who thrashes a winXP setup thats stable?

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